Controlling Parasites in Horses

Jul 13, 2020


Dr. Kenton Morgan, senior veterinarian and Equine Technical Services for Zoetis, shares his answers to some of the most common questions horse owners have about controlling parasites.

Q: When is the best time to deworm my horse?
A: Horse owners need to take advantage of the environment and deworm when parasite levels can be at their highest during the spring and fall per American Association of Equine Practitioners (AAEP) guidelines. Horses at greater risk may need more frequent anthelmintic, or deworming, treatments. Spring is the best time to treat for encysted small strongyles (strongyles in the larval stage). QUEST® Gel is a broad spectrum anthelmintic that effectively treats and controls encysted small strongyles, bots, and roundworms with just a single dose,. A recent study shows QUEST is nearly twice as effective in reducing egg counts as a double dose treatment of fenbendazole for five consecutive days.

Q: How important is dosing to an accurate horse weight?
A: Dosing based on weight is best for your horse’s safety and decreasing the risk for contributing to parasite resistance deworming. Both under- and overdosing can contribute to safety and resistance issues. It is important to dose to your horse’s weight when deworming. Download the horse weight calculator mobile application from Zoetis to easily determine the horse’s weight.

Q: Should I consult with my veterinarian about parasite control?
A: I encourage you to work with your veterinarian for advice on how to select the most appropriate dewormer for your horse. Your veterinarian can perform a fecal egg count (FEC) test to determine the necessary frequency of deworming treatments. One FEC per year is recommended for adult horses to help determine parasite levels and efficacy of the treatment. Once you have established a baseline, work together with your veterinarian to develop an individualized deworming program.

Q: Why is an FEC recommended?
A: The AAEP considers an FEC to be the best assessment of parasite burden to identify the frequency of treatment needed. By employing a fecal egg count reduction test (FECRT) with your veterinarian, you can determine whether your horse has a parasite resistance issue. To perform an FECRT, a fecal sample is collected and tested before deworming and again 14 days after deworming. This practice can help you determine when and with which product to treat for parasites.

Q: Is rotational deworming still a viable equine parasite control method?
A: This concept goes back decades and, overall, is highly discouraged. By deworming every horse every few months, horse owners can do more harm than good. Too frequent deworming can increase the risk for parasite resistance. When parasites are overexposed to certain treatments, they can become resistant, leaving fewer effective treatment options.

Q: What additional practices do you recommend to control equine parasites?
A: Make sure your horse consumes his grain and hay in a container or hay rack, not on the ground. Feeding your horse off the ground helps prevent exposure to parasites in the soil or feces. Composting manure and clipping pastures also can help control parasite populations. To help eliminate larvae, pasture rotation also is good practice, either by taking horses off the pasture or rotating in another species, such as cattle.
 
 

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